Lesson Plan 7:
Stocking Rate Calculations

Stocking Rate Activity

Name: ___________________________________

Date: ___________________

Introduction and Background Information:
Rangelands are areas of land with predominantly native vegetation made up of a mix of grasses, forbs (or wildflowers), and shrubs. Rangelands vary in their ability to produce vegetation because of different underlying soil types, amounts of moisture received, and health of the vegetation due to past management practices. Rangelands that have been moderately to lightly grazed, have soils with more organic matter, which receive more rainfall will have healthier vegetation capable of producing more forage (an amount measured in pounds/acre or kilograms/ hectare). Cattle and sheep are the predominant domestic grazers on Montana's rangelands, but big game wildlife species (such as elk, deer, and antelope) graze these same areas as well. It is important that ranchers manage how many of their animals will graze in each pasture, taking into consideration use by wildlife species, so the rangeland is not over-grazed and the vegetation remains healthy and productive for grazing each successive year. Ranchers manage so that livestock do not consume all of the forage that is available, but use a general rule of thumb to take half and leave half of the forage by weight. By leaving a portion of the forage, the remaining stubble allows those plants to maintain root reserves for survival throughout the winter and slows water movement the following spring, reducing erosion. Although the total land area may be covered with vegetation, there are some considerations to make regarding whether livestock or wildlife will use certain portions of the land. For cattle, these considerations are slope of the land and distance from water, and for elk these considerations include distance from cover and roads. The value that different types of vegetation have to the diet of cattle and elk (or grazing merit) determines its palatability (tastiness) for each animal. When calculating stocking rate, or the number of animals grazing an area of land for a certain amount of time, consider 100% of the forage available for those plant species with good grazing merit, 50% for those with fair gazing merit, and 0% of the forage weight for those plant species with poor grazing merit.

Directions:
1) Finish filling out Table 1 using information from the introduction. Three of them have been done for you as examples.

2) Using the unadjusted stocking rate equation (provided on the next page) and the given information, determine the proper stocking rate (# of animals) for the pasture for cattle only and elk only, and fill in Table 2. You will need to calculate the equation twice, once for cattle and once for elk. Drop all decimals for numbers that representanimals (e.g., 6.8 cows becomes 6 cows, and 6.2 cows becomes 6 cows). Round to tenths for all other data.

3) Next, take into consideration the spatial variables that will determine whether or not livestock and wildlife will use certain areas of the pasture (Tables 4-7) and calculate the proper adjusted stocking rate for cattle only and elk only, and then fill out Table 3 using the adjusted stocking rate equation.

4) In order to determine how many elk will be able to graze with the cattle (and vice versa) without over grazing the pasture, you will need to calculate a mixed species stocking rate using the SRm equation given below. Once you have calculated the adjusted stocking rate for cattle (or elk), take the difference between the unadjusted and adjusted values and then multiply by the animal equivalent. For example, if the unadjusted stocking rate for cattle is 100 cows and the adjusted is 60 cows, then the difference, 40 cows, is multiplied by the given value 1.54 elk/1 cow, and we get a mixed species stocking rate of elk to be 62 along with the 60 cows.

5) A tip: in order to figure out C, you will first need to figure out D (the number of days from April 1 to November 30).

6) Another tip: the Cattle SRa uses Tables 4 & 5 and the Elk SRa uses Tables 6 & 7

7) Final tip: when reading Tables 4-7, be sure you take the % Use value, not the % Reduction value.

Given Information:
Land area = 1,000 acre pasture (1 acre is approximately the size of a football field) Grazing period = 8 months (April through November) 50% of palatable forage is usable Cattle consume 780 pounds of forage per month Elk consume 546 pounds of forage per month Animal Equivalents: 1 Elk = 0.65 Cows 1 Cow = 1.54 Elk Spatial Variables: (use to select the correct information from tables 4-7) slope = 6% distance from water = 1.8 miles distance from ranch road = 0.25 miles distance from cover = 0.70 miles

Formulae:

SRa = SRu X % use for each spatial variable
SRm =(SRu SRa) X animal equivalent
SRu = unadjusted stocking rate (number of animals/land area/time period)
SRa = adjusted stocking rate (number of animals/land area/time period)
SRm = mixed species stocking rate
F = total forage that is palatable (total pounds of all plants/acre = lbs/ac.) (from Table 1)
U = use allowed (as a % of palatable forage)
A = area of pasture (acres)
C = forage consumed per day (pounds)
D = number of days the pasture will be grazed (days)